In 2011, we saw unprecedented growth of mobile malware attacks with a 155 percent increase across all platforms. Most noteworthy was the dramatic growth in Android Malware from roughly 400 samples in June to over 13,000 samples by the end of 2011. This amounts to a cumulative increase of 3,325 percent. Notable in these findings is a significant number of malware samples obtained from third-party applications stores, which do not enjoy the benefit or protection from Google’s newly announced Android Market scanning techniques.

What’s the most popular propagation vector? As always, that’s social engineering attacks — in this case, fake installers:

Fake Installers trick victims into unknowingly paying for popular applications that are normally free but have been pirated by the attackers. Victims are tricked into agreeing to terms of service of pirated applications that then send profits via premium SMS messages to the scammers. While these attacks don’t lead to complete financial ruin, they have the promise of making attackers a tidy profit a few dollars a time.

What’s the most popular malware type detected by Juniper Networks? According to its report that’s spyware applications, accounting for 63% of the total malware samples. Spyware applications can capture and unknowingly transmit data such as the GPS coordinates of the victim, text messages or the browser’s history.

Next to spyware applications, SMS trojans accounted for 36% of the total malware sample. SMS Trojans automatically and silently sent premium-rate SMS messages, with the malicious attackers earning a commission thanks to their participation in an affiliate network.